This invention relates generally to the field of devices for the prevention of accidents and personal injury. More particularly, the invention relates to a device for preventing access to an enclosure in which there is a hazardous environment.
The shelf life of harvested fruits and vegetables can be extended by storing them in an environment where the atmosphere is maintained under controlled conditions. One very important parameter in preserving produce, of course, is temperature. But other atmospheric characteristics can also affect shelf life. For example, the shelf life of many fruits and vegetables is longer if they are stored in an atmosphere that contains proportions of oxygen and carbon dioxide that are greatly less than those found in normal atmospheric air. Storage containers are now available having atmosphere control systems that can achieve and maintain not only desired conditions of temperature and humidity but also the proportions of the constituent gases of the atmosphere within the container.
Unfortunately, an atmosphere that provides the optimum shelf life for produce may also be hazardous to persons who enter the space. The optimum percentage of oxygen in the atmosphere surrounding some fruits and vegetables while in storage is on the order of five percent. A person breathing air having an oxygen content of only five percent will be unconscious within seconds and dead within minutes. Considerations of personnel safety, therefore, dictate that every effort be made to prevent the entry of persons into a space where the atmosphere is hazardous until the space can be made safe. Some readily apparent steps that can be taken include the installation of warning placards at entrances to the space and the incorporation of appropriate materials in training courses for personnel that work in and around the space. Such actions, however, may not be completely effective in preventing injury.
Some refrigerated transport containers have the capability not only to maintain a desired temperature and humidity within the interior of the container but also, through other equipment provided with the refrigeration system, to attain an atmosphere having the necessary proportions of component gases for maximum shelf life of the container contents. Such an atmosphere may be hazardous because of low oxygen levels.
What is needed is a positive means of preventing the entry of persons into an enclosed space such as a container as long as the atmosphere in the space is hazardous.